The present invention relates generally to pressure responsive valve assemblies having provision for noise attenuation. More particularly, the present invention relates to such valve assemblies adapted for use in refrigeration compressors.
Refrigeration compressors typically include pressure-actuated suction and discharge valving mounted generally in a wall of the compression chamber. It is critical to the overall operation of such a compressor to provide a sufficiently large port area to permit the flow of a maximum volume of gas within a given time period, at an acceptably small pressure drop. This concept is particularly important for refrigeration compressors employed in air conditioning systems because of the relatively high mass flow rates generally required in such systems.
In addition to maximizing the port area for a given compressor size, it is important and advantageous to reduce the weight of a moving valve member, thereby limiting the inertia effect thereof, as well as minimizing the operating noise of the valve assembly, especially in high speed compressors. In such gas compressors, it is also important to the efficiency and overall performance of the refrigeration system to minimize the reexpansion or clearance volume. Accordingly, the valving and the compression chamber wall should be configured to have a shape complementary with that of the piston, in order to reduce the volume of the compression chamber to a minimum during the reexpansion stroke without restricting gas flow. The reduction of such reexpansion volume is also greatly important in refrigeration compressors having relatively low mass flow rates, such as those frequently employed in very low temperature refrigeration systems, as well as in heat pump applications.
Examples of compressor valve assemblies calculated to address the design and performance objectives discussed above are shown in U.S. Pat. Nos. 4,329,125; 4,368,755; 4,385,872; 4,445,534; 4,450,860; 4,469,126; 4,470,774; 4,478,243; 4,543,989; and 4,548,234; as well as copending U.S. patent applications Ser. No. 714,011, filed Mar. 22, 1985, and Ser. No. 788,773, filed Oct. 18, 1985, all of which are assigned to Copeland Corporation, the assignee of the present invention, and the disclosures of which are hereby incorporated by reference herein.
Although the compressor apparatuses and valve assemblies disclosed and described in the above-mentioned U.S. Patents and copending application have superior performance and represent great advancements in the art, increasing emphasis on noise control in recent years has lead to the desirability of even further refinements in such machines in the area of noise reduction.
Traditional noise treatment approaches have frequently focused on the controlling of vibrations of the outer structure of a noise-producing device, either by way of stiffening the outer structure or related components, or by vibration damping treatments. Such approaches may be effective in structures having relatively light outer structural shells, but are frequently prohibitive because of high production costs and durability problems that frequently outweigh the improvement in noise reduction.
Another conventional approach to noise treatment involves the application of acoustical enclosures or blankets around, or the installation of mufflers on, noise-producing devices. These approaches frequently offer the advantage of a quick and relatively simple solution to noise problems, but often suffer the disadvantages of inconsistency of noise suppression performance due to enclosure leakage, interference of acoustical enclosures or blankets with the operation of the device, interference and inconvenience associated with maintenance of the device, and relatively high material costs.
As a result of the above-discussed disadvantages in conventional noise treatment approaches, more emphasis has recently been placed upon noise reduction at the fundamental source of the noise within a device or mechanism. This approach is even more desirable and advantageous when new products are being developed so that the problem of noise reduction can be addressed during the design stage. In the context of the present invention, this approach is directed to reducing noise at the noise source itself, i.e. in a valve assembly having a valve plate with an opening and a movable valve member disposed generally within the valve plate opening. Such a valve assembly also includes a retainer member fixedly connected to the valve plate and at least in part spaced therefrom such that the movable valve member is disposed between the valve plate and the retainer member. This approach to noise reduction in such a valve assembly is especially critical, since any improvement in noise reduction must be optimized in view of its effect upon the overall performance and efficiency of the gas compressor.
According to the present invention, an improved valve assembly including optimized noise attenuation includes a valve plate with a valve plate opening therethrough having a wall defining a valve seat. A valve member is associated with the valve seat and is movable between a closed position sealingly engaging the valve seat to prevent the flow of a fluid through the valve plate opening and an open position in which the movable valve member is spaced away from the valve seat to permit such fluid flow through the valve plate opening. A retainer member is fixedly connected to the valve plate and is at least in part spaced away from the valve plate to define a retainer chamber, and the movable valve member is disposed between the valve plate and the retainer member within the retainer chamber. The invention resides in providing the retainer member with a plurality of restricted flow openings extending therethrough to permit controlled flow of fluid from the retainer chamber when the valve member opens. Preferably, the retainer member substantially covers the valve plate opening, with only a minimal space, if any, between the outer peripheral edge of the retainer member and the outer peripheral edge of the valve plate opening.
The basic approach to noise reduction taken by the present invention focuses on reducing noise resulting from the impact of the movable valve member at maximum open displacement with the retainer member, or other components therebetween, which is transmitted through to the overall structure of the compressor and is frequently amplified as it radiates to the rest of the compressor's structure. The present invention seeks to overcome or at least minimize noise generated or transmitted by such impact by very quickly pressurizing the space between the movable valve member and the retainer member at the initial stage of valve opening. Such rapid pressurization of the retainer space tends to create a fluid pressure "cushion" that at least slows down the moving valve member near the end of its opening movement and thus eliminates or at least substantially minimizes the impact transmitted from the valve member to the retainer member.
In contrast to conventional wisdom, the approach of the present invention, wherein the outer peripheral spacing between the retainer member and the valve plate opening is minimized, has been empirically found to be vastly superior to that of prior valve assembly designs, wherein the retainer member was configured to be relatively narrow in order to provide a relatively large flow area between the retainer member periphery and the outer edge of the valve plate opening. Therefore, in contrast to such previous constructions, the present invention seeks to provide the above-mentioned fluid pressure cushion by minimizing the gap between the retainer member periphery and the outer edge of the valve plate opening and by providing controlled fluid communication for such fluid pressure cushioning by way of a plurality of openings through the retainer to permit the flow of fluid into the retainer chamber between the valve member and the retainer member.
The present invention also seeks to provide an optimum relationship between the retainer peripheral flow area and the size, location and number of the sound attenuation openings through the retainer member, thus providing an optimum relationship between noise attenuation and compressor efficiency. The invention provides such an optimized relationship between noise attenuation and efficiency in valve assemblies of various types, which include light-weight and quick-acting valve members in high-efficiency compressors adapted for minimizing the reexpansion or clearance volume at the valve end of the compression chamber.
Additional objects, advantages and features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.